编辑代码

class Main {
	public static int find(int[] arr, int num) {
        if(arr == null || arr.length == 0) {
            return -1;
        }
        int L = 0;
        int R = arr.length - 1;
        while(L <= R) {
            int mid = (L + R) / 2;
            if(arr[mid] == num) {
                return mid;
            } else if(arr[mid] < num) {
                L = mid + 1;
            } else {
                R = mid - 1;
            }
        }
        return -1;
    }

    public static int mostLeftNoLessNumIndex(int[] arr, int num) {
        if(arr == null || arr.length == 0) {
            return -1;
        }
        int L = 0;
        int R = arr.length - 1;
        int ans = -1;
        while(L <= R) {
            int mid = (L + R) / 2;
            if(arr[mid] >= num) {
                ans = mid;
                R = mid - 1;
            } else {
                L = mid + 1;
            }
        }
        return ans;
    }

    public static int mostRightNoLessNumIndex(int[] arr, int num) {
        if(arr == null || arr.length == 0) {
            return -1;
        }
        int L = 0;
        int R = arr.length - 1;
        int ans = -1;
        while(L <= R) {
            int mid = (L + R) / 2;
            if(arr[mid] > num) {
                R = mid - 1;
            } else {
                ans = mid;
                L = mid + 1;
            }
        }
        return ans;
    }
    
    public static void main(String[] args) {
        int[] arr = {1,2,2,4,5,7,7,8,9,10};
        // boolean aa = find(arr, 7);
        int index = find(arr, 8);
        System.out.print(index);
	}
}